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Saturday, July 16, 2011

Dramatic Climate Swings Likely as World Warms

ScienceDaily (July 15, 2011) — Dramatic climate swings behind both last year's Pakistan flooding and this year's Queensland floods in Australia are likely to continue as the world gets warmer, scientists predict.

Horn of Africa Drought ‘Set to Worsen’

The plight of millions of drought-stricken people across the Horn of Africa is set to worsen, with rains expected only later in the year and harvests months away, a top UN official warned Saturday.

Scanty or failed rainfall in the region over the past two years has already forced thousands of Somalis to flee the country and ruined the livelihoods of millions in parts of Kenya, Ethiopia and Djibouti. more...

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Fiery reds and oranges nearly covered the United States on meteorologist maps as a massive heat wave hit hard in much of the country on Saturday. Temperatures averaged up to 15 degrees above normal, with most peaks in the 90s but triple digit heat expected to strike from Montana to New Mexico, according to lead meteorologists for The Weather Channel and The National Weather Service.

Paired with oppressive humidity, temperatures will feel even hotter, as measured by the heat indexes. The NWS issued excessive heat warnings and watches for the Midwest from Texas to Canada, and heat index values over 110 degrees Fahrenheit (43 C) are possible for portions of the central and eastern United States by the middle of next week.

Locations affected are expected to see temperatures and heat indexes of up to 117 degrees (47 C), including cities like Minneapolis where that is extremely rare. "The stage is being set for a massive heat wave to develop," the National Weather service warned on Thursday.

Researchers at the Universities of Oxford and Leeds have discovered that the El Niño Southern Oscillation (ENSO), the sloshing of the warmest waters on the planet from the West Pacific towards the East Pacific every 2-7 years, continued during Earth's last great warm period, the Pliocene.

Their results suggest that swings between the two climatic extremes, known as El Niño and La Niña, may even have occurred more frequently in the warmer past and may increase in frequency in the future. Extreme ENSO events cause droughts, forest fires and floods across much of the world as well as affecting fishery production.

Reporting in the journal Paleoceanography, the team of geochemists and climate modellers use the Pliocene as a past analogue and predictor of the workings of Earth's future climate.

The Pliocene (which lasted from 5 to 3 million years ago) had carbon dioxide levels similar to the present day, with global mean temperatures about 2-3ºC higher, so it is a useful test-ground for climate research.

Lead Scientist Nick Scroxton from Oxford University's Department of Earth Sciences said: 'We know from previous studies that the mean state of the Pacific during the warm Pliocene was similar to the climate patterns observed during a typical El Niño event that we see today.

'However, until recently it was believed that a warmer Pacific would reduce the climate swings that cause the dramatic weather extremes throughout the region leading to a permanent state of El Niño. What we didn't expect was that climatic variability would remain strong under these warmer conditions.'

The team combined experiments performed on the Met Office Hadley Centre climate model, HadCM3, with the analysis of the chemical composition of lots of individual shells of small organisms, known as foraminifera.

These were collected from a deep sea sediment core in the East Equatorial Pacific, and provided a record of temperature in the upper layer of the ocean through time. They discovered that the range of temperatures experienced by these organisms during the Pliocene, was higher than what would be expected from just the seasonal cycle.

The extra variation in temperature can be explained by the additional extreme temperature swings provided by the El Niño/La Niña system.

The authors say the agreement in findings from both ocean data and modelling leaves little doubt that ENSO will persist in a warmer world. Earlier this year a team from Japan studying corals from the same period showed climatic variability in the western Pacific on a similar scale to today, questioning the idea of a permanent El Niño during the Pliocene.

This new study goes further, showing that the oscillation is Pacific-wide, and is likely to be caused by the El Niño/La Niña. This suggests that our warmer future will continue to be dogged, maybe even more regularly, by extreme climatic events.

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